INTERSTITIAL CELLS OF URODELE TESTIS 237 



first invest the lobule in a sheath one cell layer in thickness; 

 but the shrinkage of the lobule in all its dimensions and the 

 rapid increase in bulk of the cells themselves result in some of 

 them being pushed out, until the sheath becomes two or more 

 cells in thickness. The sheath maintains its position about the 

 lobule. It is seen, in a cross-section of the lobule (fig. 12) as an 

 'epithelioid ring' of varying thickness. Lobules with their 

 surrounding rings do not now press against each other. On 

 the contrary, each maintains its rounded outline, the interlobular 

 spaces outside the interstitial cell sheaths now being filled with 

 a loose meshwork of connective tissue, in which are blood vessels 

 and 'fixed' connective-tissue nuclei.^ 



In the caudal third of this same testis (of October 30th) the 

 lobules are found to be much more reduced in size and the intersti- 

 tial cells increased. Each lobule has its surrounding sheath 

 (ring in transection) of two, three, or even more cells in thickness. 

 The regularity of the rings now tends to become obscured by the 

 pressure of one against another; groups of the cells, also, tend 

 to break away from the thickened rings and occupy the spaces 

 earlier filled only by the loose connective tissue. This, in its 

 extreme, results in cords and irregular masses of cells as con- 

 trasted with the symmetrical epithlioid rings of the middle 

 of the testis. The cells, 35 to 45 ^ in their greatest diameter, 

 are irregularly polyhedral with round nuclei, and contain numer- 

 ous fuchsinophile granules and lipoid droplets, which will be 

 considered in greater detail presently. The degenerating lobules 

 and interstitial cells have, of course, been pushed somewhat 

 toward the periphery by the growing lobules, and occupy a place 

 in the testis similar to that indicated in figure 4. The yellow 

 color they now give this region in freshly cut testis is in decided 

 contrast to the pale bluish-white color of the central portion 

 occupied by the lobules of growing spermatogonia. 



^ The term 'fixed' may be applied only rather guardedly here, since one fre- 

 quently sees among these, cells with more or less resemblance to the cells of the 

 lobule sheath. The difference between cells which remain 'fixed' and those 

 which assume the interstitial cell type is probably not so much a difference in 

 the nature of the cells themselves as in the conditions they have encountered. 



